Percutaneous transluminal coronary angioplasty (PTCA) has emerged as the major viable present alternative to bypass surgery for revascularization of stenotic and occluded coronary arteries. Although transluminal angioplasty has application in peripheral artery disease, it is most widely used in the treatment of coronary artery disease. Unlike bypass surgery, percutaneous angioplasty does not require general anesthesia, cutting of the chest wall, extracorporeal perfusion, or transfusion of blood. Percutaneous coronary angioplasty is not only less invasive and less traumatic to the patient, it is also less expensive because the angioplasty patient will have a shorter hospital stay and shorter post-procedure recovery time.
Percutaneous transluminal angioplasty is performed by making a skin puncture with a specially-designed needle in one of the groins, and then introducing a guiding catheter into the aorta and coronary artery orifice. A smaller caliber catheter with a built-in inflatable and deflatable balloon of predetermined size and diameter is passed through the guiding catheter which is positioned in the orifice of a target artery. This balloon catheter (with the balloon totally deflated by negative pressure) is advanced inside the target coronary artery toward the point of obstruction in need for dilation.
The guidewire plays an essential role in leading the balloon catheter to the target coronary artery in safe and non-traumatic fashion. With the balloon portion of the catheter properly positioned inside the obstructed arterial segment, under X-ray fluoroscopic observation, the balloon is inflated by injecting contrast media mixed with saline at a pressure sufficient to overcome the resistance of the arteriosclerotic plaque of the obstructed segment.
By inflating the balloon in the stenosis multiple times over a period of between 10-30 seconds and one or two minutes (allowing blood flow between inflations), the desired dilation of the obstructed arterial segment can be achieved. After dilation, the guiding catheter, the balloon catheter (with the balloon completely deflated by negative pressure) and the guidewire are withdrawn from the artery and the patient, and the procedure is successfully terminated.
The size and diameter of the balloon to be used in transluminal angioplasty should be approximately matched to the size and native diameter of the obstructed arterial segment to be dilated. If the balloon size and diameter is smaller than the native artery, the results of balloon angioplasty are suboptimal, requiring a second dilation with a larger-sized balloon. If the balloon size is too large for the native artery, complications may occur due to arterial wall damage.
Conventional over-the-wire angioplasty catheters, with a guidewire lumen extending their entire length, permit simple guidewire exchange. Another type of angioplasty catheter has a guidewire permanently attached to the catheter at the distal end. This fixed wire, low profile catheter can be manufactured with a small overall diameter since there is no separate guidewire lumen. The guidewire in this type of catheter is referred to herein as a torquewire. Fixed wire catheters, although being preferred by many physicians because of their small diameter, have no provision for rapid replacement of either the torquewire or catheter. If, for example, balloon replacement becomes necessary once the catheter is positioned at a stenosis, the entire catheter must be removed and the balloon catheter reinserted into the artery, starting the procedure over again. Similarly, if the torquewire tip must be reshaped or replaced, the only option is removal of the entire catheter. Currently available fixed wire catheters do not have the benefit of rapid replacement.
Emergency situations can also arise during or after angioplasty. For instance, after balloon dilation, the vessel wall may collapse, requiring immediate insertion of a perfusion catheter. Accordingly, there is a need for an angioplasty catheter which retains the low distal-end profile of a fixed wire catheter while still providing the ability for rapid-exchange.